1. Field of the Invention
The present invention relates to digital broadcast, and more particularly, to non real-time broadcast services in digital broadcast.
2. Related Art
As one of the digital broadcast standards, an advanced television system committee (ATSC) prepares non real-time (NRT) services capable of providing application data services at any time after previously downloading various content files to a terminal while providing real-time broadcast using an existing broadcast standard. The ATSC uses File Delivery over Unidirectional Transport (FLUTE) (see Internet Engineering Task Force (IETF) RFC 3926) standard so as to download beforehand the content files to the terminal through an internet protocol (IP) stream.
Meanwhile, unlike typical broadcast, such as a terrestrial wave, a cable, a satellite network, or the like, that distributes contents to broadcasting, a two-way broadcast service through a broadcast network capable of implementing two-way communication represented by an internet protocol TV (IPTV) in an Internet network has newly appeared. The two-way broadcast service commonly uses multicasting or unicasting transferring contents to a terminal having a specific IP address regardless of an open network or a private network managed by a business. However, the multicasting or unicasting scheme is small in the maximum number of users that may be accessed simultaneously and coverage, as compared with the broadcasting scheme. In addition, since the multicasting or unicasting scheme does not have an independent channel that is directly managed and shares resources with multiple users in a single network, the data rate is degraded. Therefore, it is difficult to ensure quality of service (QoS) for a high definition video. On the other hand, using the two-way communication may retransmit a portion with errors and recover the portion and may provide other contents to a user or provide (for example, a video on demand (VOD) service) services only at the time of the request of the user even with the same contents.
However, a general digital broadcast is basically a broadcast scheme and is a uni-direction. When there are errors in the received broadcast contents, all the contents are not used or the contents needs to be reproduced in the state in which errors are present. These errors may occur due to a change in a physical channel of a broadcast network. In particular, the broadcast contents may be received only through a specific broadcast channel, the broadcast content cannot be received any more when the user randomly changes the channel. In addition, various services provide through a limited frequency band in the broadcast network and therefore, broadcasting through the repetition of the same contents is also limited. Therefore, there are errors in a portion of the broadcast content, there is a strong possibility that the broadcast content is not received.